1. Field of the Invention
The present invention relates to high energy loss fluid flow control devices and more particularly relates to devices sometimes known as "let down valves" used for reducing the pressure of fluids received from high pressure fluid sources as developed or used in various processes such as coal gasification, petroleum refining and the like. The fluid flow control device of the present invention is an improvement on the high energy loss fluid flow control device shown and described in a copending U.S. Pat. application Ser. No. 619,709 filed Oct. 6, 1975 which application is assigned to the same assignee as the present application.
Devices in accordance with the present invention are used in the controlled reduction of high fluid pressures down to lower pressures such as atmospheric or less and devices in accordance with the present invention are especially well adapted and designed for handling high temperature fluids including both liquids and gases that are often involved in various industrial processes. In addition, the high energy loss fluid flow control devices are useful where the fluid media contains particles of solid materials which may be abrasive and corrosive and thus have been the cause of much difficulty in prior art fluid flow control devices.
2. Description of the Prior Art
Several high pressure fluid energy loss control devices are shown in U.S. Pat. Nos. 3,451,404; 3,513,864; 3,207,181; 3,331,396; 3,426,797 and 3,514,074. Fluid flow control devices as shown in some of the aforementioned patents use parallel flow passages and these passages are sometimes formed with a plurality of disks having slots, grooves or crescent shaped passages formed therein. In the disk devices, the fluid pressure is reduced in discrete steps or increments rather than on a continuous basis and in the parallel flow devices, the pressure reduction is changed by the addition or subtraction of parallel flow paths extending between the high pressure and low pressure regions.
It is an object of the present invention to provide a new and improved high energy loss fluid flow control device and, more particularly, it is an object of the invention to provide a device of the character described which is particularly well suited for use in coal gasification systems wherein the fluid medium is supplied at high pressures and temperatures, and often contains highly abrassive solid particles such as char particles and the like.
Another object of the present invention is to provide a new and improved fluid flow control device of the character described wherein a maximum pressure reduction is obtained with a minimum of noise being generated as the fluid medium is throttled or expanded from high pressure to low pressure condition.
Another object of the present invention is to provide a new and improved fluid flow control device of the character described wherein the pressure reduction is accomplished in a continuous basis rather than by several discrete steps or increments like many of the prior art devices.
Yet another object of the present invention is to provide a new and improved high energy loss fluid flow control device wherein expansion of the fluid or flashing thereof is achieved in a helical flow path which may be increased in cross-sectional flow area as the fluid moves from the high to the low pressure regions in the device.
Yet another object of the present invention is to provide a new and improved high energy loss fluid flow control device for low level noise pressure reduction wherein a pair of members employing interfitting helical lands or threads are provided to define a helical flow path for the fluid, which path is adjustable by axial movement of one of the members relative to the other without requiring relative rotation.
Yet another object of the present invention is to provide a new and improved high energy loss fluid flow control device of the character described wherein a plurality of spaced expansion cavities are provided downstream along the helical flow path to provide discrete areas of high energy dissapation.
Another object of the invention is to provide a new and improved fluid flow control device of the character described particularly designed to have components formed of temperature resistant and wear resistant materials including ceramics and/or ceramic coated surfaces for direct contact with the flow of fluid at extremely high temperatures.